The body temperature of the desert locust Schistocerca gregaria

Summary The internal equilibrium body temperatures of hoppers (nymphs) of Schistocerca gregaria were studied in the field. The data obtained are here compared with theoretical estimates of the thermal balance resulting from the factors assumed to be concerned in heat loss and heat gain.In the field, the equilibrium body temperature of quiescent hoppers shaded from direct sunshine was up to 3.2° higher than the air temperature when the latter was about 25° or less, but was lower than the air temperature when this was above about 31°. In sunlight, body-temperature excesses increased linearly with total radiation intensity between 0.15 and 1.25 cal/cm²/min. Differences in orientation to the sun gave rise to differences in equilibrium body temperature of as much as 6°. At relatively low radiation intensities (about 0.5 cal/cm²/min) the equilibrium body temperatures were found to vary with a power of the wind speed of about 0.35. There were no demonstrable significant differences in equilibrium body temperature or rate of change of body temperature between hoppers having opposite extremes of possible coloration.Except in hoppers shaded from sunlight and those exposed to low radiation intensities there was good agreement between the observed equilibrium temperatures and those expected on theoretical grounds. This provides evidence of the relative importance of the factors concerned in thermal balance.The relation between body temperature and behaviour is discussed.

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Zusammenfassung Das innere Gleichgewicht der Körpertemperatur von vorzugsweise fünften Larvenstadien der Wüstenheuschrecke wurde unter Freilandbedingungen in Beziehung zu Lufttemperatur, relativer Luftfeuchtigkeit, Strahlungsintensität, Windgeschwindigkeit und Aktivität gemessen.Die verschiedenen Faktoren, die das Temperaturgleichgewicht der Heuschrecken beeinflussen, werden theoretisch behandelt. Die unter bestimmten Kombinationen der Umweltbedingungen zu erwartenden Gleichgewichts-Körpertemperaturen werden aus den theoretischen Werten für die verschiedenen beteiligten Faktoren errechnet und mit den unter entsprechenden Freilandbedingungen beobachteten Werten verglichen.Ohne Sonneneinstrahlung und unter relativ windstillen Bedingungen wurde bei ruhenden Larven des fünften Stadiums eine Gleichgewichts-Temperatur des Körpers gefunden, die bis zu 3,2° höher lag als die Lufttemperatur, wenn diese ca. 25° oder weniger betrug. Dieser Überschuß hatte eine abnehmende Tendenz bei Lufttemperaturen bis zu etwa 31° und über dieser Schwelle waren die Gleichgewichts-Temperaturen des Körpers im allgemeinen niedriger als die entsprechenden Lufttemperaturen. Theoretisch würde zu erwarten sein, daß unter diesen Umweltbedingungen das Temperaturgleichgewicht des Körpers in allen Niveaus annähernd der Lufttemperatur entspräche. Folglich scheint hier ein physiologischer Mechanismus zu bestehen, mit dessen Hilfe die Insekten in Abwesenheit von Sonnenschein und unter den Bedingungen schwacher Konvektion ihre Körperausgleichstemperaturen bei niedrigen Lufttemperaturen erhöhen, bei hohen senken können.Es war nicht möglich, im Freiland nachzuweisen, daß Unterschiede in der relativen Luftfeuchtigkeit irgendeinen signifikanten Einfluß auf die ausgeglichenen Körpertemperaturen in dem untersuchten Bereich (Sättigungsdefizit von 2 bis 27 mm) ausübten. Die erwarteten maximalen Differenzen der Gleichgewichts-Körpertemperaturen lagen in diesem Bereich des Sättigungsdefizits in einer Größenordnung von nur 0,5°.Unter relativ ruhigen Freilandbedingungen zeigten die Heuschrecken im Sonnenschein Körpertemperaturüberschüsse, die bei einer totalen Strahlungsintensität zwischen 0,15 und 1,25 cal/cm²/min annähernd linear anstiegen (von einem Mittel von 2–10° bei fünften Larvenstadien). Die in diesem Strahlungsintensitätsbereich gemessenen Übertemperaturen des Körpers stimmten einigermaßen gut mit Werten überein, die von anderen Untersuchern unter Laboratoriumsverhältnissen festgestellt wurden. Unter 0,40 cal/cm²/min waren die beobachteten Körpertemperaturüberschüsse im allgemeinen höher als theoretisch zu erwarten gewesen wäre. Die Körpertemperatur von Larven des ersten Stadiums nahm rascher zu als die von Larven des fünften, jedoch nur bis zu einem niedrigeren Niveau; auch das stimmte gut mit den theoretischen Vorstellungen und mit der Laborerfahrung überein. Die Einstellreaktion der Heuschrecken zur Sonne ergab beobachtete Unterschiede in der Gleichgewichts-Körpertemperatur bis zu 6° zwischen Larven des fünften Stadiums, die sich in Richtung der Sonnenstrahlen eingestellt hatten, und solchen, die im rechten Winkel zur Sonnenrichtung auf dem Boden standen; die erwarteten Unterschiede waren von der gleichen Größenordnung.Im Sonnenschein variierten die erwarteten Intensitätsproportionen zwischen der Ausgleichstemperatur und der Windgeschwindigkeit zwischen 0,5 und 0,6 mit dem Sättigungsdefizit. Bei Strahlungsintensitäten von etwa 1,10 cal/cm²/min stimmten die beobachteten Körpergleichgewichtstemperaturen engstens mit den erwarteten überein, aber bei geringeren Strahlungsintensitäten von etwa 0,50 cal/cm²/min variierten die Meßwerte mit einer Intensitätsproportion zur Windgeschwindigkeit von etwa 0,35. Darin zeigt sich möglicherweise, daß bei niederen Strahlungswerten die Körperausgleichstemperaturen zu höheren Werten tendieren als zu erwarten war.Das beobachtete Ansteigen der Körperausgleichstemperatur von ungefähr 1° bei dritten Larvenstadien und von 2–3° bei fünften Larvenstadien befindet sich in Übereinstimmung mit dem für entsprechende Umweltbedingungen errechneten.Zwischen Larven extrem entgegengesetzter Färbungstypen konnten keine Unterschiede in den Körperausgleichstemperaturen oder dem Ausmaß der Körpertemperaturänderung nachgewiesen werden.Mit Ausnahme der vor direkter Sonnenbestrahlung geschützten Heuschrecken unter relativ ruhigen Bedingungen und der Heuschrecken, die niederen Strahlungsintensitäten ausgesetzt waren, bestand eine gute allgemeine Übereinstimmung zwischen den beobachteten und den erwarteten Gleichgewichts-Körpertemperaturen. Es wurde deshalb geschlossen, daß die durchgeführten Bestimmungen Beweise für die relative Bedeutung der für den Temperaturhaushalt verantwortlichen Faktoren darstellen. Zur Erzeugung beträchtlicher Überschüsse der Körpertemperatur über die Lufttemperatur hat die Strahlung die größte Bedeutung. Für den Wärmeabfluß nach außen werden die durch Konvektion entstehenden Wärmeverluste, die insgesamt 94% oder mehr betragen, als bei weitem am wichtigsten angesehen.Einige mögliche Beziehungen zwischen Körpertemperatur und Verhalten werden besprochen.

     

A phase I trial of recombinant tumor necrosis factor (rTNF) administered by continuous intravenous infusion in patients with disseminated malignancy

rTNF was administered to 28 patients with advanced metastatic cancers by continuous intra venous infusion for 5 consecutive days every 2 weeks. The dose levels were 30, 40, 70, 110, 180 and 290 µg/M²/day. Groups of 3 patients were started at each successive dose level and then on subsequent courses treated with the next dose level through 4 escalations as tolerated. Tumor types were: colon cancer 14; adenocarcinoma of unknown primary, 2; renal cancer, 2; leiomyosarcoma, 2; lung cancer, 1; prostate cancer, 1; thymona, 1; bladder cancer; 1; parotid, 1; Kaposi's sarcoma 2; ovarian 1. Toxicities included fever and chills (usually within the first 8 hours of infusion), fatigue, headache, decreased performance status, hypotension and CNS. All patients experienced leukopenia and thrombocytopenia within 24 hours or less after start of infusion with return of baseline by 72 hours after rTNF was stopped. The fall in these counts averaged 50% and was not dose related. No major changes in liver or renal function, coagulation or blood lipids were seen. Major dose limiting toxicities were fatigue, confusion, thrombocytopenia, seizures, hypotension and decreased performance status. NK cell activity measured against K562 target cells was augmented from about 30% target cell lysis to about 70% target cell lysis over the first 7 days of treatment. Two patients, both with metastatic colon cancer showed transient, objective tumor regression which did not qualify as a partial response. One patient with ovarian cancer had a stable partial response but progressed after 13 courses of treatment. Continuous infusion of TNF can be safely administered to patients with a maximum tolerated dose of only between 30 and 40 µg/M²/day. In addition, the MTD with continuous infusion seems to be highly variable and unpredictable from patient to patient. These data suggest that continuous infusion will not be an optimal way to administer TNF.     

Responses to mitogenic stimulation of lymphocytes taken during and after pregnancy

Serial blood samples were collected during pregnancy, after delivery and several months postnatally from 28 women. The blastogenic responses of lymphocytes to varying concentrations of phytohaemagglutinin (PHA) were tested using autologous plasma or fetal calf serum (FCS) to support the lymphocyte cultures. Using FCS, the blastogenic response decreased as pregnancy progressed and remained depressed months after delivery. In contrast, when autologous plasma was used a 10-fold higher concentration of PHA was required to give optimal stimulation. Blastogenic responses were still suppressed during pregnancy but had returned to initial values by the time of delivery and were greater still in the post-partum and postnatal periods. We conclude that the inherent ability of lymphocytes to undergo blastogenesis is suppressed during pregnancy but that this is over-shadowed by a humoral effect of pregnancy plasma. The significance of these results is discussed.     

Amplification of small signals by voltage-gated sodium channels in drone photoreceptors

Summary Photoreceptor cells of the drone,Apismellifera , have a voltage-gated Na⁺ membrane conductance that can be blocked by tetrodotoxin (TTX) and generates an action potential on abrupt depolarization: an action potential is triggered by the rising phase of a receptor potential evoked by an intense light flash (Autrum and von Zwehl 1964; Baumann 1968). We measured the intracellular voltage response to a small (9%), brief (30 ms) decrease in light intensity from a background, and found that its amplitude was decreased by 1M TTX. The response amplitude was maximal when the background intensity depolarized the cell to –38 mV. With intensities depolarizing the cell membrane to –45 to –33 mV the average response amplitude was decreased by TTX from 1.2mV to 0.5mV. TTX is also known to decrease the voltage noise during steady illumination (Ferraro et al. 1983) but, despite this, the ratio of peak-to-peak signal to noise was, on average, decreased by TTX. The results suggest that drone photoreceptors use voltage-gated Na⁺ channels for graded amplification of responses to small, rapid changes in light intensity.Abbreviations TTX tetrodotoxin - V _i intracellular potential with respect to the bath - V _o extracellular potential - V _m,V _i-V _o approximate transmembrane potential - S amplitude of the voltage response to an 8.9% decrease in light intensity - N voltage noise, usually measured as root mean square voltage deviation as described in Methods     

Inhibition by excitatory sulphur amino acids of the high-affinityl-glutamate transporter in synaptosomes and in primary cultures of cortical astrocytes and cerebellar neurons

A detailed kinetic study of the inhibitory effects ofl- andd-enantiomers of cysteate, cysteine sulphinate, homocysteine sulphinate, homocysteate, and S-sulpho-cysteine on the neuronal, astroglial and synaptosomal high-affinity glutamate transport system was undertaken.d-[³H] Aspartate was used as the transport substrate. Kinetic characterisation of uptake in the absence of sulphur compounds confirmed the high-affinity nature of the transport systems, the Michaelis constant (K _m) ford-aspartate uptake being 6 M, 21 M and 84 M, respectively, in rat brain cortical synaptosomes and primary cultures of mouse cerebellar granule cells and cortical astrocytes. In those cases where significant effects could be demonstrated, the nature of the inhibition was competitive irrespective of the neuronal versus glial systems. The rank order of inhibition was essentially similar in synaptosomes, neurons and astrocytes. Potent inhibition (K _iK _m) of transport in each system was exhibited byl-cysteate, andl- andd-cysteine sulphinate whereas substantially weaker inhibitory effects (K _i>10–1000 times the appropriateK _m value) were exhibited by the remaining sulphur amino acids. In general, inhibition: (i) was markedly stereospecific in favor of thel-enantiomers (except for cysteine sulphinate) and (ii) was found to decrease with increasing chain length. Computer-assisted molecular modelling studies, in which volume contour maps of the sulphur compounds were superimposed on those ofd-aspartate andl-glutamate, demonstrated an order of inhibitory potency which was, qualitatively, in agreement with that obtained quantitatively by in vitro kinetic studies.Special issue dedicated to Dr. Elling Kvamme     

Influence of ammonium and extracellular pH on the amino and organic acid contents of suspension culture cells of Acer pseudoplatanus

The effects of supplied ammonium and nitrate on the amino and organic acid contents and enzyme activities of cell suspension cultures of Acer pseudoplatanus L. were examined. Regardless of nitrogen source the pH of the culture medium strongly affected the malate and citrate contents of the cells; these organic acid pools declined at pH 5, but increased at pH 7 and 8. Over a period of two days, ammonium had little effect on the responses of the organic acid pool sizes to the pH of the medium. In contrast, ammonium had a strong influence on amino acid pool sizes, and this effect was dependent on the pH of the medium. At pH 5 there was no increase in cell ammonium or amino acid contents, but at higher pH values cellular ammonium content rose, accompanied by accumulation of glutamine, glutamate and asparagine. Over several days, supplied ammonium led to an increase in activity of glutamate dehydrogenase irrespective of any changes in internal ammonium and amino acid contents. If the pH of the medium was allowed to fall below pH 4 in the presence of ammonium, phosphoenolpyruvate (PEP) carboxylase activity declined to a very low value over several days; at higher pH, the activity of this enzyme, and that of NAD malic enzyme and NAD malate dehydrogenase, remained substantial irrespective of whether the nitrogen source was NH⁺₄ or NO-₃.     

Short-term changes in carbon-isotope discrimination identify transitions between C3 and C4 carboxylation during Crassulacean acid metabolism

Short-term measurements of instantaneous carbon-isotope discrimination have been determined from mass-spectrometric analyses of CO₂ collected online during gas exchange for the epiphytic bromeliad Tillandsia utriculata L. Using this technique, the isotopic signature of CO₂ exchange for each phase of Crassulacean acid metabolism (CAM) has been characterised. During night-time fixation of CO₂ (Phase I), discrimination () ranged from 4.4 to 6.6, equivalent to an effective carbon-isotope ratio (¹³C) of –12.3 to –14.5 versus Pee Dee Belemnite (PDB). These values reflected the gross photosynthetic balance between net CO₂ uptake and refixation of respiratory CO₂, characteristic of CAM in the Bromeliaceae. When for the relative proportion of external (p _a ) and internal (p _i) CO₂ is taken into account, calculated p _i/p _a decreased during the later part of the dark period from 0.68 to 0.48. Measurements of during Phase II, early in the light period, showed the transition between C₄ and C₃ pathways, with carboxylation being increasingly dominated by ribulose bisphosphate carboxylase (Rubisco) as increased from 10.5 to 21.2 During decarboxylation in the light period (Phase III), CO₂ leaked out of the leaf and the inherent discrimination of Rubisco was expressed. The value of calculated from on-line measurements (64.4) showed that the CO₂ lost was considerably enriched in ¹³C, and this was confirmed by direct analysis of the CO₂ diffusing out into a CO₂-free atmosphere ( ¹³C = + 51.6 versus PDB). Instantaneous discrimination was characteristic of the C₃ pathway during Phase IV (late in the light period), but a reduction in showed an increasing contribution from phosphoenolpyruvate carboxylase. The results from this non-invasive technique confirm the observations that double carboxylation involving both phosphoenolpyruvate carboxylase and Rubisco occurs during the transient phases of CAM (II and IV) in the light period.Abbreviations and Symbols CAM Crassulacean acid metabolism - H⁺ (dawn-dusk) variation in titratable acidity - ¹³C carbonisotope ratio of plant organic material, relative to Pee Dee Belemnite (vs. PDB) - discrimination against ¹³CO₂, - p _i, p _a internal, external partial pressures of CO₂ - Rubisco ribulose1,5-bisphosphate carboxylase - PAR photosynthetically active radiation - PEPCase phosphoenolpyruvate carboxylase We are grateful for financial support in respect of research grants (GR3/5360, GR3/6419) and a studentship awarded by the Natural Environment Research Council, UK.